Thus eating merely an extra 50 more calories a day could result in a five-pound weight gain over the course of a year.

Authors Koert van Ittersum (Georgia Institute of Technology) and Brian Wansink (Cornell University) wrote: “The bigger your dinnerware, the bigger your portion. If you use larger plates you could end up serving nine per cent to 31 per cent more than you typically would.”

During an experiment, 225 student participants were asked to pour a specified amount of tomato soup into one of seven different sized bowls – three smaller, three larger and one control size.

All the participants served less than the target serving of soup into the smaller bowls and served larger amounts into the bigger bowls.

A follow-up study found the “bowl bias” was almost impossible to eliminate – apart from through changes in colour to either plates or tablecloths.

When participants were asked to serve white-sauce or red-sauce pasta on either large white or large red plates.

On average, changing the colour of the plate so it was high contrast reduced how much people served by 21 per cent and changing the colour of the tablecloth reduced servings by 10 per cent.

The study reinforces the little-know Delboeuf illusion, where people believe the size of a circle is much smaller when surrounded by a large circle than a small one.

By that rationale, when serving a food portion onto a small plate, the serving size looks relatively larger than it actually is, leading people to pile less on.

The writers concluded: "In the midst of hard-wired perceptual biases, a straightforward action would be to simply eliminate large dinnerware – replace our larger bowls and plates with smaller ones or contrast ones.”